*{
    margin: 0;
    padding: 0;
}
li{
    list-style: none;
}
.tb-promo{
    width:520px;
    height: 280px;
    background-color: aquamarine;
    margin: 100px auto;
    position: relative;
}

.prev,.next{
    position:absolute;
    top: 50%;
    margin-top: -15px;
    width: 20px;
    height: 30px;
    background-color: rgba(0, 0, 0, 0.7);
    text-align: center;
    line-height: 30px;
    text-decoration: none;
    color:#fff;
}
.prev{
    left: 0;
    border-top-right-radius: 15px;
    border-bottom-right-radius: 15px;
}
.next{
    right: 0;
    border-top-left-radius: 15px;
    border-bottom-left-radius: 15px;
}
.promoNav{
    position: absolute;
    bottom: 10px;
    width: 70px;
    height: 13px;
    left:50%;
    margin-left: -35px;
    background-color:rgba(255,255,255,0.3);
    border-radius: 7px;
}
.promoNav li{
    float: left;
    width: 8px;
    height: 8px;
    background-color: #fff;
    border-radius: 50%;
    margin: 3px;
}
/* 权重问题 */
.promoNav .selected{
    background-color: #ff5000;
}